This invention relates generally to golf ball inspection. More particularly, this invention relates to golf ball inspection for concentricity of internal components using x-rays.
While the majority of golf balls today are solid, back in the thirties, golf balls were generally only of wound construction. The wound ball was comprised of a center, windings, and a cover. One day, Philip E. Young decided to see if the wound golf ball center he was playing was concentric and asked his golfing partner, a dentist, to x-ray the ball. Sure enough, the x-ray showed that the center of his ball was not concentric. As a result, Mr. Young founded the Acushnet Process Company and began making golf balls that were all x-ray inspected for concentricity.
Heretofore, x-ray inspection of both solid and wound golf balls has been accomplished using two methods. The first method is the golden image process, which consists of taking an image of a xe2x80x9cperfectxe2x80x9d specimen (a control), placing it into memory, taking subsequent images of samples, and comparing them to the image of the xe2x80x9cperfectxe2x80x9d specimen. The differences between the xe2x80x9cperfectxe2x80x9d image and the specimen are used to determine the amount of error in the specimen.
The second method, typically for use on solid balls, includes the steps of x-raying the specimen in such a manner that both the core and the cover are displayed. X-raying the ball in this manner allows direct measurement of the thickness of the cover. This process generally requires the use of lower energy x-rays to so that the cover material can be seen clearly in the resulting image. Many times, the use of lower power causes the edges of the image to become distorted or less clear. The specimen can be doped to assist in cover detection.
Both methods may also include the step of doping the specimen so that the specimen is easier to x-ray. Doping a specimen, however, can have adverse effects on the product. The golden image process is additionally subject to error if the standard is at all less than perfect. Further, the positioning of the golf ball must be perfect. Any wobble in the fixture that holds the ball will affect the golden image test.
There are other limitations inherent in the micro focal x-ray machines that are utilized in industries such as the medical, integrated circuit, and printed circuit board industries. It should also be noted that simply using a micro focal x-ray is not sufficient to produce the sharp images required for many imaging techniques. The device for converting x-rays to visible light, called the image intensifier, must have sufficient resolution to produce a high quality image. Resolution is usually measured in line pairs per millimeter. For example, if an image intensifier has a resolution of 4 line pairs per millimeter and an optical gain of 2 it would be able to resolve an object xe2x85x9 millimeter in size.
Because of these limitations and problems, there is, therefore, a need for more suitable methods of determining the concentricity and dimensions of golf ball components using x-rays. Such a method is presented by the present invention.
The present invention is directed to A method for inspecting a golf ball comprising the steps of providing a golf ball comprising a core and a cover; abutting the golf ball against at least one flat marker; rotating the golf ball about a single axis; capturing an x-ray image of the golf ball and at least one marker; and determining the eccentricity of the golf ball.
In one embodiment, the step of determining the eccentricity comprises the step of measuring the distance from the at least one marker to an outer surface of the core as the ball rotates about the single axis. The distance between the marker and the core surface are used to determine the cover thickness. Ideally, the marker is opaque to x-rays, such as with a metal marker. Preferably, the metal is aluminum, copper, steel, titanium, or a mixture thereof.
In another embodiment, there are at least two additional markers oriented to measure different axes. The x-ray has an intensity optimized for detecting the edge of the golf ball core. The core and the marker have a first and second center and the distance between the two is calculated at predetermined intervals to determine concentricity of the core. Ideally, the x-ray has a spot size of less than about 0.035 inches by 0.02 inches, preferably, less than about 0.01 inches by 0.01 inches, and most preferably, less than about 0.005 inches by 0.005 inches. It is preferred that the x-ray has an intensity greater than the intensity required to detect the cover material such that the cover is transparent. Additionally, the cover opacity and the core opacity should be different. In one preferred core construction ,the core comprises a center and an outer core layer. The x-ray intensity is preferably between about 25 and about 75 kV, more preferably between about 30 and about 60 kV, and most preferably between about 35 and about 50 kV
The present invention is also directed to a method for inspecting a golf ball comprising the steps of providing a golf ball comprising a core and a cover; restraining the golf ball between a flat surface and a rotating concave surface; rotating the golf ball about a single axis; providing at least two reference markers abutting the cover of the golf ball, wherein a first marker is embedded in and flush with the rotating concave surface and a second marker is on an axis perpendicular to the axis of rotation; capturing an x-ray image of the golf ball; measuring a first distance between the core center and the first marker and a second distance between the core center and the second marker; and determining the true eccentricity of the golf ball by combining the first and second distances using the following formula:       E    True    =            (                        E          1          2                +                  E          2          2                    )      
where E1 is the eccentricity along the axis of rotation and E2 is the eccentricity perpendicular to the axis. The flat surface and rotating concave surface can be aligned along the axis of rotation.
A method for inspecting a golf ball comprising the steps of providing a golf ball comprising a core and a cover; restraining the golf ball against a rotating fixture; rotating the golf ball about a single axis; providing at least two reference markers abutting the cover of the golf ball, wherein a first marker is embedded in the rotating fixture and abuts the cover, and a second marker is on an axis perpendicular to the axis of rotation; capturing an x-ray image of the golf ball; measuring a first distance between the core center and the first marker and a second distance between the core center and the second marker; and determining the true eccentricity of the golf ball by combining the first and second distances using the following formula:       E    True    =            (                        E          1          2                +                  E          2          2                    )      
where E1 is the eccentricity along the axis of rotation and E2 is the eccentricity perpendicular to the axis. The golf ball may be restrained against the rotating fixture with clamps.